STEREOISOMERIC INVERSION OF (25R)-and (25S)-3α, 7α, 12α-TRIHYDROXY-5β-CHOLESTANOIC ACIDS IN RAT LIVER PEROXISOME

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The stereoisomeric inversion of (25R)-and (25S)-3α, 7α, 12α-trihydroxy-5β-cholestanoic acid (THCA) in rat liver peroxisome was studied. After incubation of an isomer of THCA-CoA thioester with a peroxisomal fraction, 5β-cholestanoic acids were extracted and optical antipodes were separated and determined by LC/APCI-MS. The transformation of (24E)-3α, 7α, 12α-trihydroxy-5β-cholest-24-en-26-oic acid (Δ²⁴-THCA) formed by acyl-CoA oxidase was also analyzed by GC/NICI-MS. Rapid enzymatic epimerization from either direction was observed prior to biotransformation into (24E)-Δ²⁴-THCA.